[mcstas-users] Simulation of ESS testbeamline instrument at HZB

Wed Dec 14 09:02:33 CET 2016

Hi again,

Agreed, this is a good tip. Perhaps implemented as instrument input parameters Lmin and Lmax so that the range is variable (to be able to study if anything unwanted makes it through your complex chopper arrangement...).

Another few tips:

You can find parameters for the HZB sources in Source_gen - see http://www.mcstas.org/download/components/sources/Source_gen.html<http://www.mcstas.org/download/components/sources/Source_gen.pure.html>
- That should take you closer to the intensities that you will measure at the ESS test beam line.

As I understood you will likely soon add a sample description? In that case a SPLIT right before the sample position will boost your final detector statistics. Single_crystal and PowderN provide "guesses" at good SPLIT numbers, for other samples you will currently have to make a good guess yourself. :-)

As far as I know the instrument is running a prototype of the DAQ and reduction software to be used at ESS? In that case you could at some point consider implementing Mantid event monitors, see https://github.com/McStasMcXtrace/McCode/wiki/McStas-and-Mantid

Best and good luck simulating,

Peter

Technical University of Denmark

Department of Physics
Neutrons and X-rays for Materials Physics
Fysikvej

Building 307<x-apple-data-detectors://1/0>

DK-2800 Kongens Lyngby<x-apple-data-detectors://1/0>

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Den 14. dec. 2016 kl. 07.22 skrev Kim Lefmann <lefmann at nbi.ku.dk<mailto:lefmann at nbi.ku.dk>>:

Dear Alaa,

A quick read through the modified code tells me that you can use a much smaller energy interval from the source (I take that you like to produce a monochromatic pulse eventually?). This will speed up your simulations a factor > 10.

best, Kim

On 12/13/2016 11:08 AM, Peter Kjær Willendrup wrote:
Dear Alaa,

Thank you for your email - I had a quick look at your instrument file and made some adjustments - see attached.

1) I Assume that in cases where your DiskChoppers are AT the same place they make up an “assembly” or GROUP? In these cases you should also
- Include the first of these choppers in the GROUP also -  done in the attached
- For each individual chopper assembly, there has to be a unique GROUP name, hence I created in total 5 GROUPS

2) Are BC_1 and BC_2 maybe meant to be counter-rotating? In that case I think you are missing a sign-change on the frequency parameter of one of them?

3) I added a new input parameter Chopper_in that via the WHEN keyword can disable all of the choppers beyond the first counter-rotating set.
- I also had to put a “dummy” arm component pr. chopper group to make sure there is a SCATTER when the group is deactivated by the WHEN.

We are now in the situation that neutrons are transported both when the choppers are in and out - further optimisation quite likely necessary (only 8 rays out of 1e7 makes it to the sample when choppers are in…), but this at least gives you a way forward. :-)

Hope this helps, and good luck moving further.

Best,

Peter Willendrup

Peter Kjær Willendrup
Senior Research Engineer, Special Advisor

DTU Physics

<mime-attachment.gif>

Technical University of Denmark

<mime-attachment.gif>

Department of Physics
Fysikvej

Building 307

DK-2800 Kongens Lyngby

Direct +45 2125 4612

Mobil +45 2125 4612
Fax +45 4593 2399

pkwi at fysik.dtu.dk<mailto:pkwi at fysik.dtu.dk>

On 13 Dec 2016, at 10:16 , Ala'a Al-Falahat <alaa.falahat at gmail.com<mailto:alaa.falahat at gmail.com>> wrote:

Dear users,

I have started to simulate the ESS Test Beam Line at HZB center (please find the attached files to show the instrument in details).
I have generated proper code for it (see instrument file attached below) but I get a warning message that no neutron could reach to some component when I try to get a result,

Hopefully, you can find a solution on that.
For more information don't hesitate to contact me.

The first attached you should find at the page number 2 the whole instrument.
The second attached in appendix A , you should find the instrument in details.
The third attached you will find the instrument file I did.

with many wishes
Alaa

---------------------------------------------------------------------------------------------------------------------------

Institute of Applied Materials
Helmholtz-Zentrum Berlin for Materials and Energy
Hahn-Meitner-Platz , 1
14109 Berlin
Germany

<(First attached)The wavelength frame multiplication chopper system for the ESS test beamline at the BER II reactor.pdf><(second attached)The test beamline of the European Spallation Source – Instrumentation.pdf><V20TestBeamLineV2.instr>_______________________________________________
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